Harvested slurry - estimating cells per ml

Discussion in 'Beginners Brewing Forum' started by Tal Orbach, May 21, 2019.

  1. Tal Orbach

    Tal Orbach Member

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    So, I think I did something to make my slurry not layer properly.
    Is there any way to estimate roughly how many billion cells per ml I have here?
    [​IMG]
     
  2. Trialben

    Trialben Well-Known Member

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    I go by 1billion/ml myself so if that's a 500ml jar 250billion ish half full. But I'm no yeast pro that's for sure and your slurry looks just like mine does all mixed up and brown with no distinct yeast layer with bits of hop material in there too it looks.
     
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  3. Tal Orbach

    Tal Orbach Member

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    So we're talking 1B/ml of the whole sludge at the bottom, yes?
     
  4. Nosybear

    Nosybear Well-Known Member

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    What you're asking is tough without actually counting the cells using a microscope and hemocytometer. There was an answer to a question posed by Yours Truly in Zymurgy a year or so back on that very question. I didn't get a good answer from them, either. The yeast calculators like the one here probably give you the best estimates without actually counting cells.
     
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  5. J A

    J A Well-Known Member

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    I use the Mr Malty yeast calculator in conjunction with the Yeast pitch calculator here. I've had good results. The Mr.Malty allows for factoring in the age of the slurry. Slurry that's a week old has a much higher viable yeast count than one that's been stored for 2-3 months. The process definitely requires some good estimating and you get used to judging your own particular slurry by appearance and assessing performance. There are some good
    There's a big difference in the quality of slurry harvested with different methods. I harvest yeast from my conical Unitank and can get a several pints of very high-count slurry that way. When I re-use yeast from a carboy, it's very good but since all the sediment has mixed together it tends to be less pure and I assume it's slightly less dense and calculate accordingly.
     
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  6. Trialben

    Trialben Well-Known Member

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    So .5 billion/ml then JA? I've seen the yeast youse guys pull out the bottom of them conicals and am envious.
     
  7. J A

    J A Well-Known Member

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    At least a full 1b/ml for clean slurry out of the conical and it packs tight. For other slurry I may go down to .75 or .5 depending on age and condition. Mr Malty shows about 1B/ml at about a month of age for average slurry so I factor in that the BF calcuator estimate is a little low for yeasts that are really fresh and a high for yeasts that have some age on them.
     
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  8. Tal Orbach

    Tal Orbach Member

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    Forget age and viability, and forget about dense pure yeast slurry, like you can get from a conical fermenter. My question is about the yeast density this not-so-pure slurry in the photo had when I harvested. Of course I can't really get an accurate number or even a relatively accurate estimate, but what would be a safe assumption here?
     
  9. Trialben

    Trialben Well-Known Member

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    I think JA pointed out .75B/ml as above for not pure yeast Slurry probably a safe bet. Are we talking lager or Ale yeast if Ale you got plenty in surplus.
     
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  10. Tal Orbach

    Tal Orbach Member

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    Ale, but they've been waiting for a couple of months, so I don't know that I do have plenty in surplus... (I do have another jar with about the same amount, so...)
     
  11. J A

    J A Well-Known Member

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    I can't actually see your image. There's just a big blank space in your post. If I could see it I could probably opine as to the specifics.
    I'm assuming that it's typical stuff saved from the bottom of a carboy. If it has a lot of hop stuff and/or protein goo and it's freshly harvested after sitting no more than a couple of weeks in a fermenter at reasonable temps, then maybe assume .5 B/ml to be safe.
     
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  12. Tal Orbach

    Tal Orbach Member

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    Hmm... Can you see it in this link: https://photos.app.goo.gl/gt6gATEc4Wvk5MZK7
     
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  13. J A

    J A Well-Known Member

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    That's better.
    That sample has a lot of hop and protein goo and is probably relatively low in viable cells. I wouldn't count on more than .5 billion per milliliter. If that's a pint jar you have about a.25 liters of thick trub and you're probably cutting it close for a pro-brewer level pitch on an ale even if it's really fresh. It it's a quart jar and you have a half liter of thick trub, you should have a good, strong pitch if it's fresh and a reasonable pitch if it's been sitting for over 6 weeks or so. That's based on a beer of maybe 1.060.
    As long as it was pulled out of the fermenter as soon as the beer was at FG or shortly thereafter, it should be good yeast to work with. If you let it sit in the primary fermenter for 3 weeks or so while the beer aged and cleaned up, it would be less viable.
    Good luck with it, YMMV. ;)
     
  14. Tal Orbach

    Tal Orbach Member

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    I have two jars, both are a bit under a liter, meaning in total I have about 700 ml of this trub. It was harvested from the fermenter about 1 week post FG, if I remember correctly, which was about 8 weeks ago.
    What would you say is a safe estimate for the cell count?
     
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  15. Mase

    Mase Well-Known Member

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    Based on 8 weeks, you should be about 50-60% viable, maybe a little more. Wyeast (which I use), has a shelf life of about 6 months. Have you tried the yeast calculator in this site?
     
  16. J A

    J A Well-Known Member

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    #16 J A, May 22, 2019
    Last edited: May 22, 2019
    If I was using it, I'd feel safe counting on around 250 billion cells. That's enough for a pro-brewer pitch on 5 gallons of 1.060 ale. Just curious...what yeast strain, what gravity was the beer you harvested from and what are you brewing with it? Those are all factors I'd take into consideration. For instance, I pitched what I figured might be a bit of a low pitch (based on age of the slurry) on a 1.070+ Belgian and normally I wouldn't re-use that yeast. It was such a strong and clean fermentation though, I saved it because I know that the yeast is pretty healthy even after that beer. I'd pitch it again on a lower gravity batch.
     
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  17. Tal Orbach

    Tal Orbach Member

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    It's S-04.
    The beer it was harvested from had an OG og 1.060 (FG 1.012).
    I want to pitch it in a beer that will have an OOG around 1.040 - 1.045.
     
  18. J A

    J A Well-Known Member

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    S-04 is pretty robust yeast. The gravities shouldn't be a problem. Assuming we're talking 5 gallon batches, you have more than enough yeast. You might even pitch just one and see if it really goes strong and add the other if it's weak or stalls out.
    Oxygenate your wort well and add some yeast nutrient to your boil.
     
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  19. Tal Orbach

    Tal Orbach Member

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    So should I not make a starter?
    What if don't have yeast nutrient?
     
  20. J A

    J A Well-Known Member

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    If you're making a starter, one of those jars of slurry will be fine. You can use dead yeast for nutrient. There's probably enough malt protein and dead yeast in your slurry for nutrient.
     
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